DAC build TDA1541A/SAA7220P/B *will take som time* - Page 75 - diyAudio
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Old 3rd January 2014, 08:49 PM   #741
ctef is offline ctef  Bulgaria
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Join Date: Nov 2011
Location: Bulgaria, Sofia
Now I see. This capacitance multiplier is from Rod Elliotts site. I follow and some other his projects.
Any how. Let me report what is done.
In my treasures I found a suitable trafo. Now I have about 310V DC without any voltage multipliers. For now didn't make and capacitance multiplier. Use just 2x200uF. And hum is much less then before. Even without and inductance for now. For filament I use about 30,000uF, but there is a little ripple - about 0,1V, under load.
Well, the test.
I used my original Coupled Cathode Follower with ECC83, at 1mA. Now hum is neglect able.
Sound is very clear and open. Comparing to Russian tube, it is soft indeed, but sound like behind a blanket. There are much voice, guitars, details, dynamic with 83. The world is presence. Maybe miss a little softness, but is good for now, much better than before. Now, with this big gain, I can try to reduce the I/V resistance and under 33ohms.
I'm going to test and my SE circuit with 83.
For a moment I forgot about harmonics.
No jokes, will be good, if I can measure them. But no chances. May try only with DEQ analyzer.
And something more. When watching at oscilloscope and generator, I see very small sparks, only at high resolution levels. No sound effects.

Last edited by ctef; 3rd January 2014 at 08:52 PM.
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Old 3rd January 2014, 11:46 PM   #742
erin is offline erin  Australia
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Yes the picture is from Rod's website. Im glad your hum is reduced.
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Old 6th January 2014, 05:36 PM   #743
ctef is offline ctef  Bulgaria
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Few words, more.
I redid my circuit, to this. Sound is not changed, or seem so.
But, this and my first circuit from The Valve Wizard, to works good, needs one resistor on the output, to the ground. Before the capacitor, after doesn't work. I use 100K. The problem is, that without it, the trace on scope, is double, with dots.
Hum. Let say again, the levels are low, but I wish to decrease it more.
The hum is 50Hz. When unplug the AC power, and run just at capacitors charge, it doesn't disappear. So, I think it is not from the power supply. This is some antenna-effect. The output capacitors was with metal body. When touch, hum increases. I exchanged them with red WIMA MKS. They don't react to touch.
And at the output I have now 1.4V RMS, with 23ohms I/V resistance.
Click the image to open in full size.
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Old 6th January 2014, 10:17 PM   #744
erin is offline erin  Australia
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Have you tried placing your circuit inside a metal chassis?
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Old 7th January 2014, 06:07 AM   #745
ctef is offline ctef  Bulgaria
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Not yet. But other my circuits are in PC supply boxes.
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Old 8th January 2014, 07:08 AM   #746
ctef is offline ctef  Bulgaria
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Now I tried circuit in metal box, but hum is the same
A friend told me, this is because of the Hi impedance of tube- ECC83.
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Old 8th January 2014, 02:11 PM   #747
ctef is offline ctef  Bulgaria
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A step backward, I went back to 6N24P, after a little increasing of current, but no improvement. The same soft sound. Hum also exists, less then ECC83, but exists. Let me say, however, I listen at bi amping system, and amps are at fully open volume, 80W, no attenuators! I attenuate from the Foobar player. Well, but in the same conditions, OpAms are dead silent.
Any way. Once I heard the sound of ECC83, I must get such sound. The way doesn't matter for me. I'm not in love with the tubes. If I get the same result with "sands", why not?
The bad is, I have no reliable source for genuine OpAmps. Ebay is hazard.
However, What do you think about Pedja Rogics Diamond circuit?
I'm not familiar with electronic, so let me ask a few questions.
May we manipulate the gain of Diamond and how?
May we use it with I/V resistor, too, instead of this transistor 2sk170bl?
The circuit is not complex, so what do you advice me?
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